Authentication problem with login manager gdm or lxdm using ldap account credential

[stefano malini]

Hi,
i've problems trying login from login manager of my ubuntu 10.10 client 
using ldap user credential. Ldap server is squeeze.
Only using a shell after login with my account on the machine i can 
login with ldap account credential but not with login manager as gdm or 
lxdm.

this is the output of auth.log:

Apr  4 15:50:51 dello gdm-session-worker[3414]: 
pam_succeed_if(gdm:auth): error retrieving information about user nslcd_proc
Apr  4 15:51:04 dello pkexec[3421]: gdm: The value for the SHELL 
variable was not found the /etc/shells file [USER=root] [TTY=unknown] 
[CWD=/] [COMMAND=/usr/sbin/gnome-power-backlight-helper --set-brightness 15]
Apr  4 15:51:17 dello gdm-session-worker[3414]: pam_unix(gdm:auth): 
check pass; user unknown
Apr  4 15:51:17 dello gdm-session-worker[3414]: pam_unix(gdm:auth): 
authentication failure; logname= uid=0 euid=0 tty=:0 ruser= rhost=
Apr  4 15:51:17 dello pkexec[3423]: gdm: The value for the SHELL 
variable was not found the /etc/shells file [USER=root] [TTY=unknown] 
[CWD=/] [COMMAND=/usr/sbin/gnome-power-backlight-helper --set-brightness 15]
Apr  4 15:51:42 dello pkexec[3429]: gdm: The value for the SHELL 
variable was not found the /etc/shells file [USER=root] [TTY=unknown] 
[CWD=/] [COMMAND=/usr/sbin/gnome-power-backlight-helper --set-brightness 15]

What is the problem?